package kr.hkit.powerjava.chapter23;

class Counter {
	private int value;

	public synchronized void increament() {value++;}
	public synchronized void decreament() {value--;}
	public synchronized void prnCounter() {System.out.println(value);}
}

class SharedThread extends Thread {
	Counter sharedCounter;

	public SharedThread(Counter sharedCounter) {
		this.sharedCounter = sharedCounter;
		this.start();
	}

	@Override
	public void run() {
		int i = 0;
		while (i < 20000) {
			sharedCounter.increament(); // counter 1증가
			sharedCounter.decreament(); // counter 1감소
			if (i % 40 == 0) {
				sharedCounter.prnCounter();
				try {
					sleep((int) (Math.random() * 2));
				} catch (InterruptedException e) { }
				
			}i++;
		}
		
	}
}

public class CounterTest {
	public static void main(String[] args) {
		Counter c = new Counter();
		new SharedThread(c);
		new SharedThread(c);
		new SharedThread(c);
		new SharedThread(c);
	}
}
